The present invention relates generally to semiconductor manufacturing technology, and more particularly to a method and system for monitoring a dimensional change of a pattern for a mask or reticle used in a semiconductor manufacturing process.
Precision and accuracy are two important factors in a process control for semiconductor manufacturing. A method that accurately measures the dimensions of a pattern for a mask or reticle is particularly important for an etching process. Conventional measurement methods, such as plasma intensity method, current bias of inductively coupled plasma (ICP) reactors method, by-product method, are often used to detect the endpoint of an etching process. A basic concept of these conventional methods is to project a beam on a laminated structure undergoing an etching process, and detect a change of intensity of the beam reflected therefrom, when the upper layer of the structure is completely removed. However, these methods do not provide information about critical dimensions of a pattern, and a phase change after an electromagnetic wave passing through the pattern. Such information is particularly important for controlling the quality of the mask or reticle.
Conventionally, the critical dimensions are measured by a scanning electron microscopy (SEM) or other optical metrology tools. A phase change can be measured by atomic force magnifier (AFM), or other optical metrology tools. One shortcoming of the metrology tools is that they are designed to operate after an etching process is completed. Thus, they cannot be used with etching equipment for in-situ measurements.
Desirable in the art of semiconductor manufacturing technology are methods and systems capable of monitoring information, such as a dimensional or phase change, during an etching process.